DIFFERENTIAL INDUCTION OF CYTOCHROME-P-450 ISOZYMES BY RIFAMPICIN IN THE CHINESE-HAMSTER, CRICETUS-GRISEUS

Treatment of male and female Chinese hamsters with rifampicin at intra peritoneal doses of 25 and 50 mg/kg did not increase the cytochrome P- 450 content of the liver except for a 1.3-fold increase in male hamste rs at a dose of 50 mg/kg. Enhancement of the activities of erythromyci n N-demethylase and testosterone hydroxylases, except for 15 alpha-hyd roxylation, was observed in the livers of both male and female hamster s treated with rifampicin at both doses. Western blot analysis reveale d that rifampicin caused no change in the content of CYP3A subfamily p roteins in the liver, whereas changes in that of CYP2A subfamily prote ins were evident.